Centrifugal casting apparatus



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Jan. 8, 1957 H. D. BOGGS CENTRIFUGAL CASTING APPARATUS 9 Sheets-Sheet 8 Filed Dec. 11, 1950 mmm INVENTOR flail/KW V ATTORNEYS.

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United States Patent CENTRIFUGAL CASTING APPARATUS Herbert D. Boggs, Tulsa, Okla., assiguor to H. D. Boggs Company, Ltd., Omaha, Nebr., a limited partnership Application December 11, 1950, Serial N 0. 200,193

1 Claim. (Cl. 18-4) This invention relates to new improvements in apparatus for forming pipe, particularly, cast pipe of large diameter made of plastic material reenforced with filaments, yarns, fabrics, or the like.

Field of invention Plastic materials, both of the thermosetting and thermoplastic type have been employed in the past for the formation of tubing and pipe. However, such use of plastic materials has generally been restricted to making relatively small pipes and tubes, i. e., four inches or less, because of limitations imposed by the fabricating apparatus which has been available heretofore. For example, small diameter pipe and tubing have been formed generally by extrusion of a plastic mass in screwstuflertype machines or related apparatus.

The advantages of the use of plastic pipe, such as its good corrosion resistance, relatively low heat conductivity, lightness in weight, ease of installation, and the like, make it desirable to produce plastic pipe of relatively large size, e. g., three inches I. D., or more. Numerous attempts have been made in the past to accomplish this either with existing machines or specially designed equipment. However, commercially feasible and usable methods and apparatus for accomplishing this have not been provided prior to this present invention.

Upon first inspection, it would seem that the formation ing a large size plastic pipe, particularly of the filamentreenforced variety. For example, it is necessary, in order to provide suflicient structural strength in the large diameter to incorporate some reenforcing material with the plastic. For all practical purposes, this prevents the use of standard type extruding equipment. Mandrel winding has been tried, but is generally unsatisfactory, because consistenly leak-proof pipe cannot be made by this method. Furthermore, established centrifugal casting methods and apparatus cannot be employed for the purpose, because they result in a pipe having the reenforcing material unevenly distributed through the pipe, so that the resulting tubular structure does not have adequate strength.

Objects (1) The provisionof plastic pipe centrifugal casting machines which can be used to form cast pipe having filamentous reenforcing material'substantially uniformly 'ice distributed throughout the cross section of the pipe giving a leak-proof product of high bursting strength.

(2) The provision of such machines which can be operated by substantially unskilled persons in semi-automatic fashion with a minimum of attention.

(3) The provision of such machines in which a plurality, e. g., six or more, pipes may be formed at one time.

(4) The provision of new equipment for the intro duction of plastic-forming material into a centrifugal casting mold for the formation of filament reeenforced plastic pipe.

(5) The provision of semi-automatic means for loading, conveying and unloading pipe casting molds in pipeforming machines.

(6) The provision of new units for holding pipe casting molds in operating position within a pipe-forming machine.

(7) The provision of new methods for the casting of plastic pipe having filamentous material uniformly distributed throughout for the purpose ofreenforcing the pipe.

(8) The provision of new methods for casting of reenforced plastic pipe which may be carried out on a commercial basis for the production of large diameter pipe having good structural properties.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

General description These objects are accomplished according to the present invention'by first loading a casting mold with a web, mat, or fabric of filamentous material which may contain no plastic impregnant or may contain a small amount of plastic material. When the web has been properly positioned around the inner periphery of the mold or flash, the mold is revolved at relatively high rate in order to impose a centrifugal action upon the contents. At this point, plastic material is introduced into the mold upon the inner surface of the web contained in the mold and this is done in such a manner and with control of the viscosity of the plastic-forming material and speed of spinning of the mold, that the introduced material is uniformly distributed across the inner surface of the web and penetrates uniformly through the web toward the outside thereof and against the inner periphery of the casting flask. At the same time, the mold and its contents are subjected to the action of heat or other conditions which'will bring about the rather rapid polymerization of the plastic-forming material. The subjection of the flask and its contents to the polymerization conditions and the spinning is then continued until a substantially solid pipe is formed.

In order to aid those skilled in the art to more fully understand the general method for forming pipe ac cording to this present invention and to enable them to conduct the process and assemble the necessary apparatus, a preferred form of apparatus for use in the invention is described below in conjunction with the accompanying drawings, in which:

Figure 1 is a plan view showing the preferred form of the new apparatus with a portion of the machine omitted from the drawing for the sake of clarity and understanding.

Figure 2 is an end view of the machine shown in Figure 1, with, however, the mold conveying unit, omitted in Figure 1, properly displayed.

Figure 3 is a side view of the apparatus shown in Figure 2.

Figure 4 is an enlarged, sectional side view of the lower right-hand corner of Figure 3, with, however, a modified form of mold conveying unit substituted for the conveyor of Figure 3.

Figure 5 is a sectional side view of the same portion of the apparatus shown in Figure 4 with the various elements, however, in the loading and unloading position.

Figure 6 is a plan view, partly broken away, showing details of the mold conveyor unit of the apparatus as less clearly shown in Figures 2 and 3.

Figure 7 is a side view, partly in section, of the conveyor unit shown in Figure 6.

Figure 8 is a view partly in elevation and partly in section of a mold or casting flask of the type used in forming pipe in the machine, illustrated in the preceding figures.

Figure 9 is a side view of the mechanism used to introduce the plastic-forming material into the pipe mold subsequent to positioning of the molds in the casting machine.

Figure 10 is an enlarged, sectional view of the pump and pump drive portion of the apparatus shown in Figure 9.

Figure 11 is a top plan view of the apparatus shown in Figure 9.

Figure 12 is a plan view of the lay-out of the footings and the like for the apparatus shown in the preceding figures.

Figure 13 is a partially enlarged, sectional plan view of the roller drive portion of the casting machine.

Figure 14- is an end view, partly in section, of the portion of the machine illustrated in Figure 13.

Detailed description As can be seen, by reference to Figures 1 to 3, the new apparatus consists fundamentally of a mold support and drive unit 2, a mold conveyor unit 4, a mold holddown unit 6 for holding molds in position during the casting operation, polymerization means 8 for subjecting the molds and the contents thereof to polymerization conditions during the casting operation and distributor means 16 for introducing plastic-forming material into the molds of flasks when properly located within the pipe-forming machine.

The mold supporting unit 2 comprises a rectangular frame 12 having a parallel pair of end members 14 and a pair of side U channel strips 16. A pair of cross members comprising the U-shaped channel units 18 also form a portion of the stationary frame 12.

At spaced distances on the cross channels 18, there are fixed pairs of bearings 20. Long axles 22 are iournallcd in some of the bearings 20, while shorter axles 24 are journalled in the remaining pairs of the bearings .29. Similarly, pairs of bearings 26 are fixed upon the end frame members 16 and in these are journalled short axles 28. A plurality of rollers 30 having metal shoes 32 are fixed upon the short axles 24 and 28 and the long axles 22.

In operation, molds 34 rest upon the rollers 30, as can be seen in Figure 4, and are caused to turn or spin by driving the rollers 30, which are attached to the long axles 22, through rotation of the axles 22.

The means for rotating the axles 22 can be understood best by reference to Figures 13 and 14. As shown, the prime mover for the rollers is the electric motor 36 which is connected through the shaft 33 and the flexible coupling 40 to the pulley assembly 42 consisting of a pair of fixed bearing members 44, a shaft 46, and three pulleys 48, 50 and 52. A mul'ti-strand belt 54 connects the pulley 42 to the pulley 56 carried upon the shaft 58 which is journalled in the bearings 60 and 62. Also.

4 keyed to the shaft 58 is a second pulley 64 around which the multi-strand belt 66 runs to the pulley 68 which is fixed upon the axle 22.

Similarly, the belt 70 runs on the pulley 50 and pulley 72, the latter being keyed to the shaft 74 which is jour nalled in the bearings 76 and 78. A second pulley fit) is fixed to the shaft 74 and carries the belt 82 to drive the pulley 84 fastened to the axle 22. Likewise, a third axle 22 is driven by belt 86 which runs around the pulley 52 and the pulley 88 fastened to the axle 22. Base plates 90 and 92 and angle members 94 and 96 are slotted so as to permit proper adjustment of the bearings and pulleys to allow for satisfactory running of the machinery.

The conveyor unit 4 serves to transport molds across the machine by picking them up from a delivery rack 5 8 for positioning upon the rollers 30 and also to remove them from the machine onto the rack 160.

As can be seen by reference to Figures 6 and 7, conveyor unit 4 comprises vertically movable ramps 1S2 formed of two U channels 194 properly spaced by spacer members 106.

These ramps 102 are supported through clevice connectors 108 and 110 by the pistons 117. of the hydraulic cylinders 114, which also serve to raise and lower the ramps during the mold conveying operation of the ma chine.

The transfer of the mold across the machine accomplished by the conveyor 116 which consists of chain 118 which runs around the drive sprockets 120 and has the spaced rollers 122 fastened thereon by suitable links 124. The conveyor is driven through the sprocket 126 which is fastened to the same shaft as one of the sprockets 120. A chain 123 runs around the sprocket 126 and the sprocket 130 which, in turn, is fixed on the shaft 132, coming from the speed reducer unit .134 driven by the motor 136. The chain conveyor on the other ramp 102 is driven through the action of the tubular shaft 138 which is connected to the shaft 140 through the universal joint 142. The opposite end of the shaft 13% connects to the sprockets 144 through the universal joint 146.

The preferred form of mold conveyor is shown in Figures 6 and 7, but another usable form of conveyor is illustrated in Figures 4 and 5 which consists of the ramps 148 which hold the sprockets which carry the chain conveyor 152, having mold positioning lugs 154. fastened thereon.

The mold hold-down unit 6 comprises a rectangular frame composed of side members 1.56 and cross members 158 and 160. Rollers 162 having shoes 164 are journallcd in the channels and by raising and lowering the frame, these rollers can be brought in contact with the top side of the molds 34 (as shown in Figure 4), in order to hold molds in casting position within the machine.

The rollers 162 and related assembly are raised and lowered through the side units composed of the side frames 166 having uprights 16S, cross beam 170 and braces 172 and 174. Pulley support plates 176 are fasten to the top of the side frames 166 and in these plates are journalled the pulleys 178 and 18%. Over these pulleys pass the cables 182, one end of which is fastened to the counterweights 184 and the other end to the side frame members 1.56.

In order to raise and lower the roller 162 in a horizontal position, a special mechanism is used to drive the pulleys 180. This consists of an elevating motor 136 connected to the sprocket 188 through the belt or chain 190. The sprocket 188 is keyed to the shaft 192 which drives the gear box 194 and, in turn, the belts 196. Consequently, the elevating motor 186 can move all four pulleys at the same speed and insure level raising and lowering of the rollers 162 and the associated frame. Proper movement of the rollers is also accomplished by providing guide rollers 198 on each end of the side frames 156. These rollers run against the guides 200 formed in the side frames 166. Stops or rests 202 are fixed on the side frames 166 in order to prevent the side members 156 from descending too far.

The polymerization means 8 can take a number of forms, e. g., steam coils, infra-red lights, or other heating means or the like could be used. However, in the preferred form in the apparatus, as illustrated, this means 8 consists of a series of elongated gas burners 204 which are positioned parallel to one another and to the axles of the rollers 30. The burners are slender enough to fit between rollers 32 and across conveyor channels 104 so a flame comes out of the beam. The burners are installed to allow the chain 122 to pass and are located substantially mid-way between the roller axles 22 and 24, as the case may be. The gas burners are fed by the supply pipes 204 and flexible pipe 205a (connected to flexible hose, automatic control valves and acclimatic thermopile, not shown).

The plastic-forming material distributor means 10' consists fundamentally of horizontal trackways 206 and 207, located at each side of the machine, spray tubes 208 and a wheeled carriage 210, means 212 for'feeding plastic material into the spray tubes 208 and means 214 for moving the wheeled carriage 210. The track 206 has a flat top surface while track 207 is beveled to receive the beveled wheels 211 to properly guide the carriage.

The spray tubes 208 are made of such length as to be able to extend substantially half-way into the casting molds when the Wheeled carriage 210 is brought as close toward the molds as possible. Suitable spray heads 216 are fixed to one end of the tube-$ 208, while the tubes are supported at the other end by brackets 218 fastened to the channel units 220 which, in turn, are fixed upon the wheeled carriage 210 comprising two side members 222, two end members 224, a center beam 226 and two central support beams 228 and 230.

The end members 224 of the carriage 210 have extending brackets 232 and 234 which support axles 235 in a position which is adjustable through the adjustment bolts 236 and lock nuts 238 and 239.

A plurality of triangularly-shaped flanges 240 are welded to the I-beam 226 and at the front of these there are fastened bearings 242, while at the back the bearings 244 are fixed. At spaced intervals to the flanges 240 and in line with the tubes 208, centrifugal fluid pumps 246 are fastened on the I-beam 226. Between the pumps 246 and the bearings 242 run drive shafts 248 to which are keyed drive sprockets 250. 1

Iournalled in the bearings 244 is a drive shaft 252 which carries a series of sprockets 254 and around these sprockets 254 and the corresponding sprockets 252 are belts or drive chains 256. About mid-way on the shaft 252 is a multi-section sprocket 258 which is operatively connected to the gear reduction box and drive motor unit 260 through the drive sprocket 262 and drive chains 264.

The pumps 246 are supplied with plastic-forming liquid through the supply line 266 which is joined through a flexible coupling 267 to a source of plastic-forming solution or liquid (not shown). The outlet side of the pumps is connected through the nipples 268 and flexible unions 270 to the back-end of the tubes 208. The movement of the wheeled carriage 210 and supported tubes 208 toward and away from the castingfmolds when positioned upon the rollers 30 is accomplished by the drive chain 272'. This chain runs between the sprockets 274 and 276 under the tension pulleys 2'78 and 280. The sprocket 274 is driven by the shaft 282, beveled gears 284 and 285, shaft 286, sprocket 287 and motor 288.

In order to provide sufficient room for the proper displacement of all parts of the new machine and to minimize vibration, the various parts of the machine are preferably supported upon special foundations. These are illustrated in Figure 12 and consists of rectangular footings 289, hydraulic cylinder pits 290, motor and pulley shaft pit 292, drain 294 and a pit 296 for the motor used to operate the mold conveyor 4.

Operation Having now described the essential portions of the new machines, a brief description of the method of use of the new machines and the new procedures for casting plastic pipe in accordance with this invention may be given.

The molds used in the casting operation can be of various types, but a preferred form is shown in Figure 8. This consists of a tubular section 298, provided with end flanges 300 and flanged guide wheels 302 fixed such as by set screws 304 toward the inside of the tubular portion 298. End caps 306 are held on the mold with set screws 308 with ring paper seals 310 positioned over the mold end to hold the liquid in the molds at the ends.

To begin the casting operation, a suitable filament web or fabric is inserted into the mold. If a woven fabric is used, the insertion can be accomplished by rolling the fabric up, slipping the roll into the mold and then pushing it against the insides of the mold by some guide member or by air pressure. The same method can be employed for inserting an unwoven web of fabric material or such a web can be positioned in the mold by blowing stable fibres into the mold.

Such molds, properly loaded with reenforcing filamentous material, are brought up to the machine loading position on the ramp 98. The rollers 162 are raised to their topmost position by operation of the motor 186, pulleys 180 and associated parts. The mold conveyor unit 4 is then elevated high enough by the hydraulic pistons 112 to bring the chain mold carriers 116 on level with the ramp 9%]. As the carriers 116 are moved by action of the motor 136, sprockets 126 and 120, the molds are dropped-from the ramp 98 into position on the carrier 116 and moved into the machine above the rollers 30. At this point, hydraulic pistons 112 are lowered moving the ramps 104 and the supported molds 34 down over the rollers 30. As the ramps 104 pass below effective level of the rollers 30, the molds drop into position between the paired rollers.

The hold-down rollers 162 are now lowered by operation of the motor 186 until the entire weight of the rollers 162 and associated members 156 and 160 bear upon the molds 34.

At this point, motor 186 is stopped and motor 36 turned on, in order to start the spinning of the molds,

Plastic-forming material is then introduced into the molds. This is accomplished by running the wheeled carriage 210 as far in toward the side frames 166 as possible through operation of the motor 286 and the chain drive 272. This brings the spray heads 216 on the opposing tubes 208 to the center point of the molds. With the molds spinning through the drive of the motor 36, retraction of the tubes 208 upon the carriage 210 is started. This retraction is accomplished at a slow constant speed and, as soon as it starts, plastic-forming material is sprayed out of the end of the tubes through the action of the pumps 246 and the associated drive elements. As can be seen, since each of the pumps is driven at the same rate of speed which is controlled through the gear box and motor unit 216, the rate of spraying of the plastic-forming material on the inside of the molds is controlled. The viscosity of the plasticforming material can be varied and, actually, it is desirable to use a resinous material which has been partially polymerized. This is desirable so that controlled penetration of the resinous binder will take place as the pipe mold spins at a high initial velocity.

Right after the pipe molds are loaded in the machine and before the spraying of plastic material takes place, the gas burners are turned on in order to heat the molds. With the molds in a heated condition, the material sprayed into the molds begins to penetrate the fiber mat immediately. This combined with a high speed causes a full and good penetration of the fiber core with ideal wetting and surrounding of each fiber. In this way, and through the control of the weight of spray and the withdrawal of the spray tubes, distribution of the plastic material in the mold and about the fiber reenforeing material can be accomplished. Only one passage of the spray tube may be used, but unusual results have been obtained using two passages of the spray tube. In the first passage, 80% of the total plasticforming material is introduced, while the remaining 20% is introduced on the second pass. This second portion helps to control the polymerization by consuming exothermic heat of polymerization from the previously sprayed material and, thus, helps to obtain a craze-free, void-free pipe wall. Three or more passes of the spray unit may be employed, but this is generally unnecessary. After impregnation, rate of the spinning is reduced so that it does not extremely counteract the natural shrink of the resin during cure so the good mold release can be obtained.

After the resinous material has been loaded into the molds, the spinning and heating of the molds is continued for the length of time that experience shows is required to substantially polymerize the plastic material and form the cast pipe. At this point, the gas burners are cut off and the hold-down rollers 162 and associated parts are raised. Then, the conveyor unit 4 is elevated, picking the pipe molds up off of the rollers 30 and lifting them to the level of the outgoing ramp 100. Here, the chain carrier 116 is again put in operation so that the molds are again conveyed across the machine and roll out on the ramp 100.

As soon as all of the molds are removed, the conveyor unit 4 is elevated up to the level of the incoming ramp 98 and the operation as described above is repeated.

No particular attention has been given in the description to specific plastic-forming materials to be used in forming the pipe, since the equipment and procedures are applicable to practicably any known polymerizable substance. However, actual experience has shown that thermosetting addition-type polymerizable compound, e. g., polyfunctional acrylic resins of the polyhydric alcohol type, diallyl dicarboxylic acid esters, maleic acid esters, and related thermosetting compositions are particularly useful in the process. Any suitable filamentous material may be used, e. g., nylon, Orlon, asbestos, vinyl resin filaments, cotton, wool, silk, linen, wire, but glass fiber and similar inorganic fibres are preferred. If desired, known modifications may be employed, such as use of mold lubricants, but this is generally unnecessary.

Conclusions The invention, as described in detail above, provides a unique method for forming fib1$-l611f01'6d, plastic pipe of large diameter, at the same time eliminating most of the defects of previously known procedures for forming large size plastic pipe. Thus, it permits the pipe to be made in a relatively short period of time without any great need for skilled supervision. The pipe that is made, moreover, is leak-proof, of high quality, and has good structural strength, since the plastic material is reenforced by fibrous webs or filaments which are uniformly distributed within the plastic body of the pipe and not concentrated on one side or other of the pipe to give poor tensile and bursting strength.

The new procedures and apparatus are applicable to most known types of plastic-forming materials and reenforcing filaments, this general applicability being a noteworthy feature of the development.

I claim:

A machine for casting a section of plastic pipe reenforced with a fiber web which comprises a plurality of parallel, equally spaced axles commonly journalled upon a stationary rectangular base, a plurality of rollers fixed upon said axles, a motor for rotating some of said axles, belt means operatively connecting the drive shaft of the motor to a plurality of said axles, a vertical support frame positioned adjacent one end of said base, a second vertical support frame positioned adjacent the opposite end of said base, flanged pulleys carried upon the top of said support frames, counterweighted cables which run over said pulleys, a rectangular frame supported for vertical movement by said cables having guide rollers on the sides thereof which roll in channels contained in said support frames, a plurality of rollers commonly journalled in said rectangular frame, means to drive said pulleys to raise and lower the cable supported frame to bring the said second rollers into contact with molds carried by said first rollers, a pair of parallel channel members vertically movable between said stationary frame and said cable supported frame, a plurality of hydraulic piston members supporting said channel members from beneath to raise and lower them, a pair of sprocket wheels journalled upon each end of the channel members, a pair of continuous conveyor chains mounted upon said sprocket wheels to convey molds horizontally across said machine, longitudinal gas burners located below said first rollers midway between said axles and parallel to, horizontal trackways at each side of said base running parallel to said axles, a wheeled carriage on each trackway, tubes supported in an elevated position by one end upon said carriages, spray heads on the free ends of said tubes, liquid pumps connected to the supported ends of said tubes, means for driving all said pumps upon the carriage at the same speed, and means for moving both said carriages toward and away from said base at the same constant velocity.

References Cited in the file of this patent UNITED STATES PATENTS 1,572,445 Nichols Feb. 9, 1926 1,783,094 Moore et al Nov. 25, 1930 1,786,586 Walter Dec. 30, 1930 1,927,467 Morgan ..2 Sept. 19, 1933 2,002,701 McWane May 28, 1935 2,023,381 Hume Dec. 3, 1935 2,038,861 Stussi Apr. 28, 1936 2,161,968 Lyons et a1 June 13, 1939 2,252,219 Trotzke Aug. 12, 1941 2,285,370 Staelin June 2, 1942 2,334,294 Stevens Nov. 16, 1943 2,334,648 Ransburg et al Nov. 16, 1.943

FOREIGN PATENTS 21,626 Great Britain Dec. 11, 1913 267,002 Great Britain Mar. 1, 1927 658,257 France Ian. 25, 1929 

